Safety mechanism for preventing accidental deployment of a utility knife blade

ABSTRACT

A safety mechanism for a utility knife, including a razor blade mounted in a blade holder slideably mounted in a blade chamber in the housing. A first blade holder includes an arm extending therefrom with an engaging surface thereon. A second blade holder includes a tab extending therefrom. When either blade holder is deployed from the housing, the tab contacts the engaging surface, thereby preventing deployment of the other blade until the original blade is retracted.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/624,310, filed Nov. 2, 2005, which is incorporated by reference inits entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of cutting tools,and more specifically to a safety mechanism for preventing theaccidental deployment of a utility knife blade.

BACKGROUND OF THE INVENTION

Utility knives that incorporate retractable, replaceable razor bladesare well known in the art. Utility knives are very versatile, enjoyingpopularity with the professional construction worker, the domestichandyman, and the amateur hobbyist alike. Utility knives generallyinclude a retractable razor blade mounted within a protective handle orhousing. The blade is fastened to a support structure such as a bladecarrier or blade pusher, which extends through the surface of thehousing. In operation, the blade is extended by sliding the blade holderforward. One deficiency of the prior art designs is that the blade maybe inadvertently deployed, becoming a safety hazard. For example, if theblade holder catches on a pocket or a tool belt or is jostled by anothertool in a toolbox, the blade may be deployed unbeknownst to the user. Anunwary user reaching for a utility knife with the blade deployed caneasily receive a severe cut.

There have been attempts in the prior art to address this problem. Forexample, U.S. Pat. No. 5,890,294 to Keklak et al. discloses a lockingsafety utility knife having an operating lever that deploys a blade whensqueezed and a ratchet-like locking mechanism releasable by manipulation(depression) of a cam located at the end of the knife. However, theKeklak et al. device still exhibits the problem of accidentaldisengagement of the safety if the cam is accidentally depressed,allowing the knife to accidentally open and deploy the blade. Moreover,the cam is located on the end of the knife, increasing the likelihood ofaccidental depression.

Other known utility knives known in the art have sliding blades that arelocked by blade holders that must be depressed as they are slid forwardto engage the blade. Again, since the unlocking force and the deployingforce may be resolved into a single angular force acting upon the bladeholder, accidental release of the blade can readily occur if the bladeholder catches on the user's clothing or on another tool.

There is therefore a need in the art for a safety mechanism for autility knife that cannot be accidentally disengaged through the simpledepression of a switch or cam. Furthermore, for utility knives withseparate controls for deployment of each of two blades, there is a needfor a safety mechanism that prevents deployment of both blades at thesame time. The present invention satisfies both of these needs.

SUMMARY OF THE INVENTION

The present invention relates to a safety mechanism for a utility knife.The utility knife includes a knife blade mounted in a blade holder thatmay move between a retracted, blade-stowage position in the housing anda deployed position wherein the blade at least partially protrudes fromthe housing. The blade holder includes an actuating lever portionprotruding from the housing. Two such blade holders are provided suchthat blades may be deployed from either end of the knife. In oneembodiment, a first one of the blade holders includes an arm extendingtherefrom in the direction of the second blade holder. The second bladeholder has a tab that engages the arm of the first blade holder, suchthat interaction between the arm and the tab prevent one blade holderfrom being deployed while the other blade holder is deployed.

In one form of the invention, a safety mechanism for a utility knife isdisclosed, comprising: an elongated housing having an apertured anteriorend and an apertured posterior end; an anterior blade chamber formedwithin the anterior end of the housing and aligned with the anterioraperture; a posterior blade chamber formed within the posterior end ofthe housing and aligned with the posterior aperture; an anterior bladeholder slideably mounted in the housing and having an anteriorblade-engaging portion positioned in the anterior blade chamber, and anarm operationally coupled to the anterior blade-engaging portion andextending substantially toward the posterior blade chamber, the armhaving a contacting surface; a posterior blade holder slideably mountedin the housing and having a posterior blade-engaging portion positionedin the posterior blade chamber, an extension operationally coupled tothe posterior blade-engaging portion, and a tab coupled to the extensionand adapted to selectively engage the contacting surface; an anteriorblade mounted in the anterior blade holder; a posterior blade mounted inthe posterior blade holder; wherein the posterior blade holder isadapted to move between a recessed position wherein the posterior bladeis completely within the housing and a deployed position wherein theposterior blade extends partially outside of the housing; wherein theanterior blade holder is adapted to move between a recessed positionwherein the anterior blade is completely within the housing and adeployed position wherein the anterior blade extends partially outsideof the housing; wherein the tab engages the contacting surface when oneof the respective anterior and posterior blade holders are in therespective deployed position; whereby if the anterior blade holder is inthe deployed position, then the posterior blade holder cannot be movedfrom the recessed position; and whereby if the posterior blade holder isin the deployed position, then the anterior blade holder cannot be movedfrom the recessed position.

One object of the present invention is to provide an improved utilityknife. Related objects and advantages of the present invention will beapparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the preferred embodiment of the presentinvention.

FIG. 2 is an exploded side perspective view of the embodiment of FIG. 1.

FIG. 3 is a side elevational view of the blade holder of the embodimentof FIG. 1.

FIG. 4 a is a side sectional view of the embodiment of FIG. 1 with theblade recessed and locked.

FIG. 4 b is a side sectional view of the embodiment of FIG. 1 with theblade recessed and unlocked.

FIG. 4 c is a side sectional view of the embodiment of FIG. 1 with theblade deployed.

FIG. 5 is a side elevational view of a first type of second embodimentblade holder of the present invention.

FIG. 6 is a side elevational view of a second type of second embodimentblade holder of the present invention.

FIG. 7 is an exploded perspective view of a second embodiment housing ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring now to FIG. 1, there is illustrated a first embodiment of thepresent invention, indicated generally at 20. With reference to FIG. 2,the utility knife 20 includes a housing having an anterior end 24 and aposterior end 26. Preferably, the housing 20 has 180-degree rotationalsymmetry about a midpoint 25. In other words, the preferred embodimentis a double-acting utility knife 20 adapted to deploy a razor blade fromeither end 24, 26, embodiments having different numbers of blades arelikewise contemplated.

Referring now to FIG. 2, the anterior and posterior ends 24, 26 of thepreferred embodiment have apertures 28 a-b formed therein. The apertures28 a-b are preferably slots, although they may have any convenientconfiguration. Chambers 30 a-b are formed in the housing, each adaptedto receive a blade holder 32 (see FIGS. 3 and 4 a-c). Safety channels 34a-b are also formed in the housing adjacent the blade chambers 30 a-b.Safety channels 34 a-b are formed extending respectively from end walls35 a-b and open respectively into blade chambers 30 a-b. A razor blade(illustrated in phantom at 36 in FIGS. 3 and 4 a-c) may be removablycoupled to each blade holder 32.

FIG. 3 illustrates blade holder 32. Blade holder 32 is adapted to hold arazor blade 36 in the blade-engaging portion 40, while actuating leverportion 42 extends out above the blade-engaging portion 40. Blade holder32 also includes a tab or safety-channel engaging portion 44, whichpreferably extends at a substantially 90-degree angle from actuatinglever portion 42. Safety channel engaging portion 44 is adapted toslidingly engage one of the safety channels 34 a-b when blade holder 32is operationally positioned in housing 22.

FIGS. 4 a-c illustrate blade holder 32 slidingly positioned in housing22 and in which a blade 36 has been operationally coupled. While FIGS. 4a-c detail a blade holder 32 positioned to deploy a blade 36 from theanterior end 24 of utility knife 20, it is understood that theillustrated process equally applies through symmetry to a blade deployedfrom the posterior end 26. FIG. 4 a illustrates blade holder 32occupying recessed position 46, with safety channel engaging portion 44slidingly engaged in safety channel 34 a. Blade holder 32 is preventedfrom moving towards anterior end 24 (and blade 36 is prevented fromexiting slot 28 a) by the end wall 35 a of safety channel 34 a lockinglyengaging safety channel engaging portion 44.

FIG. 4 b illustrates blade holder 32 being disengaged from safetychannel 34 a. A disengaging force vector acts on blade holder 32 suchthat channel engaging portion 44 is slid away from end wall 35 a, downsafety channel 34 a, and into blade chamber 30 a, thus releasing bladeholder 32 and enabling blade holder 32 and held blade (illustrated inphantom at 36) for deployment.

As is shown in FIG. 4 c, blade 36 is deployed by sliding blade holder 32towards anterior end 24 of utility knife 20 while maintaining sufficientforce on the safety channel engaging portion 44 (by depressing actuatinglever portion 42) to prevent it from re-engaging safety channel 34 a.Blade (illustrated in phantom at 36) in deployed position 50 partiallyextends through slot 28 a.

Blade holder 32 is preferably formed from spring steel, but may be madeof any material that will exert a biasing force against deformation. Thespring steel exerts a biasing force on tab 44, pushing it into channel34 a as soon as it is aligned with channel 34 a. Tab 44 must be pushedagainst the biasing force to remove tab 44 from channel 34 a in orderfor the blade to be deployed.

A second embodiment of the present invention is illustrated in FIGS.5-7, with continuing reference to FIGS. 1-4. Items in the secondembodiment that are substantially similar to like items in the firstembodiment are given like reference designators. The second embodimentutility knife of the present invention provides a safety feature thatprevents accidental (or intentional) deployment of both blades at thesame time.

As shown in FIG. 5, in order to provide this feature, a first bladeholder 132 in the second embodiment is substantially identical to theblade holder 32, but includes an arm 60 depending therefrom in thedirection of the second blade holder. The arm 60 includes a widenedportion 62 at the distal end thereof. Portion 62 includes an engagingsurface 62 a.

A second blade holder 232 of the second embodiment is illustrated inFIG. 6. Second blade holder 232 includes an extension 64 with a tab 66extending substantially perpendicular therefrom. Tab 66 is sized andpositioned so as to contact engaging surface 62 a of the first bladeholder 132 if there is an attempt to deploy both blade holders 132,232at the same time. As shown in FIG. 7, a channel 70 is formed in thecentral wall of the utility knife housing in order to allow passage ofthe arm 60 from the first blade holder 132 to the second blade holder232.

In operation, when first blade holder 132 is retracted, second bladeholder 232 may be fully deployed before tab 66 contacts engaging surface62 a. Once tab 66 is in contact with engaging surface 62 a, first bladeholder 132 may not be deployed because the interaction between tab 66and engaging surface 62 a prevents such movement. Similarly, if firstblade holder 132 is deployed first, engaging portion 62 a will come intocontact with tab 66 once first blade holder 132 is fully deployed. Thiscontact will then prevent deployment of second blade holder 232 untilfirst blade holder 132 is retracted. Consequently, both blades of theutility knife cannot be deployed at the same time.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiments have been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

1) A safety mechanism for a utility knife comprising: an elongatedhousing having an apertured anterior end and an apertured posterior end;an anterior blade chamber formed within the anterior end of the housingand aligned with the anterior aperture; a posterior blade chamber formedwithin the posterior end of the housing and aligned with the posterioraperture; an anterior blade holder slideably mounted in the housing andhaving an anterior blade-engaging portion positioned in the anteriorblade chamber, and an arm operationally coupled to the anteriorblade-engaging portion and extending substantially toward the posteriorblade chamber, the arm having a contacting surface; a posterior bladeholder slideably mounted in the housing and having a posteriorblade-engaging portion positioned in the posterior blade chamber, anextension operationally coupled to the posterior blade-engaging portion,and a tab coupled to the extension and adapted to selectively engage thecontacting surface; an anterior blade mounted in the anterior bladeholder; a posterior blade mounted in the posterior blade holder; whereinthe posterior blade holder is adapted to move between a recessedposition wherein the posterior blade is completely within the housingand a deployed position wherein the posterior blade extends partiallyoutside of the housing; wherein the anterior blade holder is adapted tomove between a recessed position wherein the anterior blade iscompletely within the housing and a deployed position wherein theanterior blade extends partially outside of the housing; wherein the tabengages the contacting surface when one of the respective anterior andposterior blade holders are in the respective deployed position; wherebyif the anterior blade holder is in the deployed position, then theposterior blade holder cannot be moved from the recessed position; andwhereby if the posterior blade holder is in the deployed position, thenthe anterior blade holder cannot be moved from the recessed position. 2)The safety mechanism of claim 1 further comprising a channel between theanterior blade chamber and the posterior blade chamber, wherein the armpasses through the channel. 3) The safety mechanism of claim 2 furthercomprising a wall separating the anterior blade chamber from theposterior blade chamber, whereby the channel is formed in the wall. 4)The safety mechanism of claim 1 further comprising: an anterior safetychamber formed within the housing and oriented substantially parallel tothe anterior blade chamber; a posterior safety chamber formed within thehousing and oriented substantially parallel to the anterior bladechamber; the anterior blade holder having an anterior safety chamberengaging portion adapted to engage the anterior safety chamber; and theposterior blade holder having a posterior safety chamber engagingportion adapted to engage the posterior safety chamber; wherein theanterior and posterior safety chambers are adapted to releasably engagethe respective anterior and posterior safety engaging portion of therespective anterior and posterior blade holders when the respectiveanterior and posterior blade holders are in the recessed positions;wherein the respective anterior and posterior safety chambers arefurther adapted to prevent motion towards the respective anterior andposterior ends of the respective anterior and posterior engaged safetyengaging portions; and wherein the respective anterior and posteriorblade holders must be pushed into the housing and away from therespective anterior and posterior apertures to release the respectiveanterior and posterior safety engaging portions from the respectiveanterior and posterior safety chambers, enabling the respective anteriorand posterior blade holders to move into the deployed positions. 5) Thesafety mechanism of claim 4 wherein the respective anterior andposterior safety engaging portions are positively biased into therespective anterior and posterior safety chambers. 6) The safetymechanism of claim 1 wherein the respective anterior and posteriorapertured ends are slits. 7) A utility knife comprising: a housing; afirst blade holder; a second blade holder; and a safety mechanism whichoperationally couples the first blade holder and the second bladeholder; wherein the first blade holder is adapted to move between afirst recessed position and a first deployed position; wherein thesecond blade holder is adapted to move between a second recessedposition a second deployed position; wherein if the first blade holderis in the first deployed position, then the second blade holder cannotbe moved from the second recessed position; and wherein if the secondblade holder is in the second deployed position, then the first bladeholder cannot be moved from the first recessed position. 8) The utilityknife of claim 7 wherein the safety mechanism comprises: an arm coupledto the first blade holder, the arm having an engaging surface; a tabcoupled to the second blade holder and adapted to engage the engagingsurface when one of the respective first and second blade holders are inthe respective first and second deployed positions. 9) The utility knifeof claim 7 further comprising: a first blade chamber formed within thehousing; a second blade chamber formed within the housing; and a channelbetween the first blade chamber and the second blade chamber; whereinthe first blade holder is substantially located within the first bladechamber, the second blade holder is substantially located within thesecond blade chamber and the safety mechanism passes through thechannel. 10) The utility knife of claim 9 further comprising a wallwhich separates the first blade chamber from the second blade chamberwhereby the channel is formed in the wall. 11) The utility knife ofclaim 9 further comprising: a first safety channel formed within thehousing and in communication with the first blade chamber; a secondsafety channel formed within the housing and in communication with thesecond blade chamber; the first blade holder having a first tab that isbiased to engage the first safety channel when the first blade holder ismoved into the first recessed position; and the second blade holderhaving a second tab that is biased to engage the second safety channelwhen the second blade holder is moved into the second recessed position;wherein the first blade holder must be moved toward the first recessedposition before the first blade holder can be moved into the firstdeployed position; and wherein the second blade holder must be movedtoward the second recessed position before the second blade holder canbe moved into the second deployed position. 12) The utility knife ofclaim ii wherein the respective first and second tabs are positivelybiased into the respective first and second safety chambers. 13) Autility knife comprising: a housing; a first blade holder; a secondblade holder; a first blade mounted in the first blade holder; a secondblade mounted in the second blade holder; and a safety mechanism whichselectively couples the first blade holder and the second blade holder;wherein the first blade holder is adapted to move between a firstrecessed position wherein the first blade is completely within thehousing and a first deployed position wherein the first blade extendspartially outside of the housing; wherein the second blade holder isadapted to move between a second recessed position wherein the secondblade is completely within the housing and a second deployed positionwherein the second blade extends partially outside of the housing;wherein if the first blade holder is in the first deployed position,then the second blade holder cannot be moved from the second recessedposition; and wherein if the second blade holder is in the seconddeployed position, then the first blade holder cannot be moved from thefirst recessed position. 14) The utility knife of claim 13, wherein thesafety mechanism comprises: an arm operationally coupled to the firstblade holder, the arm having a contacting surface; and an extensionoperationally coupled to the second blade holder and adapted toselectively engage the contacting surface when one of the respectivefirst and second blade holders are in the respective first and seconddeployed positions. 15) The utility knife of claim 13, furthercomprising: a first blade chamber formed within the housing; a secondblade chamber formed within the housing; and a channel between the firstblade chamber and the second blade chamber; wherein the first bladeholder is substantially located within the first blade chamber, thesecond blade holder is substantially located within the second bladechamber and the safety mechanism passes through the channel. 16) Theutility knife of claim 15, further comprising a wall which separates thefirst blade chamber from the second blade chamber whereby the channel isformed in the wall. 17) The utility knife of claim 15, furthercomprising: a first safety channel formed within the housing and incommunication with the first blade chamber; and the first blade holderhaving a first tab that is biased to engage the first safety channelwhen the first blade holder is moved into the first recessed position;wherein the first blade holder must be moved toward the first recessedposition before the first blade holder can be moved into the firstdeployed position. 18) The utility knife of claim 17 wherein the firsttab is positively biased into the first safety chamber. 19) The utilityknife of claim 15, further comprising: a second safety channel formedwithin the housing and in communication with the second blade chamber;the second blade holder having a second tab that is biased to engage thesecond safety channel when the second blade holder is moved into thesecond recessed position; wherein the second blade holder must be movedtoward the second recessed position before the second blade holder canbe moved into the second deployed position. 20) The utility knife ofclaim 19 wherein the second tab is positively biased into the secondsafety chamber.